Carburetor



Feb. 4, 1930. P. s. nca y A 1,746,094

cARURnroR Fuga Dec. 1e 1924 I l In the drawings:`

Patented 4Feb. 4, 1930 fg- UNi'rub vsfr'. .'11-r; s oFFlcE.

' i I l -rERoIvAI- s. rior., orcnreneo, A:muratore:` l I 'I I ucannuanroa.,

Appucuon nea,` recenter. 18,' 1924. serial mf'rsszs. o

` -rThe--purposeof this invention iste provide l an improvedform and'const/'ruct-ion ofV acar-` buretcr for internal combustion engines` t adapted to automatically suit the fuel mix* 5 ture to varying engine speeds and loads, and also automatically aiford quik acceleration ;l

and with these functional improvements to be'- economical of. construction and convenient' for installation. J

Figurel is a plan'view of a carburetor embodying. this invention.

' Figure 2 is a partly sectional side elevation of the same section being made axially of the fuel mixture conduit through apart of its extent.

, Figure 3 isf Figurel.

Figure 4 is a section at the line 4.-4 on 2 Figure 2. y

.Figuref is a detail section in the plane of the lines 5--5 on Figure 1 and 5"*--58L on FigurefLg v Figure 6 is a detail section at the plane of a section at the line 3-3 on the lines 6-6 on Figure 2 and 6-6 on Figure Y c 4 through -to the bottom 1n a 11ne causing saldl 5, intersecting at the point 6X on Figure 5.

. The structure shown in the drawings comprises the following parts formed as an integral casting, viz: First, the fuel'mixture 3 conduit, 10, designed to extend horizontally when in service,having a constriction at 11 giving its cavity Venturi form; second, the float bowl or lvel-gover ning chamber, v12, extending vertically transversely of the fuel the constricted Venturi portion, and third, a nexus, 15, 'between the -fuel mixture conduit and the loatbowl, which nexus aifords pas- 40 lsage and mounting for'the needle valve hereg 45e-19:'The fuelinlet passage has a seat, 20, at

its inner end for the valve, 21, controlled by `the' float,22; and at the outer end of said inlet passage there isscrewed thereinto a nipple, 24',- forronnecting a fuel supply'pipe, leadl l5o ing from the fuel source (not shown) for mixture conduit laterally thereof, oppositev vsupplyingthe oatibowl by any vpreferred method. u u The liquid fuel duct from the iioat bowl coinprises the outlet passage, 26, from said bowl, l

and the discharge into the fuel mixture conduit seen 'at 27, entering said conduit sub stantially at the Venturi constriction, 11. The'out'let passage, 26, from the float bowl is formed bydrilling across the nexus, 15, near the lower end thereof into the lower part of the bowl,the outer end of the bore being permanently closed by a plug, 28. The d ischarge passage, 27, into the' venturi isformed bv drilling from the' opposite side of the venturi, the bore through' said opposite side 65 being permanently closed by a plug, 29. Be-

tween the outlet, 26, from the bowl and the dischargepassage, 27, into the venturi of the fuel mixture conduit, the fuel duct comprises a trap chamber, 30, formed in the nexus, 15, through which trap chamber the needle valve,

31, extends from the upper end of said nexus: This tra chamber and theseat and guide bearing ihr the needle valve are formed by first boring the nexus from the upper end in two diameters and "threading the last lcounterbore at the upper 'end portion for receiving a plug, 35, threaded at its upper end for screwing into the threaded counterbore, t, and having an exterior shoulder at its lower end for stopping and seating liquid-tight at the lower end of the nexus. Said plug has an annular groove, 36, a cross bore, 37 at that roove and an' axial bore, 38, from the upper 90 end of the plug into said cross bore, con` stituting the connection Afor fuel flow from the outlet, .26, intotheloweend of the trap chamber, 30. Before inserting the plug, 35,

there is inserted through the trap chamber 9I and made fast at its upper end in the lower 'end of the original first mentioned bore which is couuterbored to form the trap chamber below the intersection of said bore with the duct, i 27, a Sleeve,l 39, which when thus made fast x00 at its upper end terminates at its lower end a short distance above the plug, 35. This sleeve, it will be seen, renders the chamber, 30, a trap as abovedesignated, inl which under certain-conditions the liquid fuel Will be' accumulated as hereinafter described.'

The original bore in the upper part of the nexus leading out from the top of the trap chamber is counterbored from the upper end to receive a stuffing box, 43, and isthreaded below said counterbore to engage the stem, 44, of the needle valve, 31, which, below the threaded part of said stem, is reduced in diam tion, 11, and has its stem, 51, provided outsidethe fuel mixture conduit with an operating lever, 52, and the usual operating connections (not shown), an abut-ment, 53, being provided for encounterof a lug, 54, projecting from the hub of the lever, 52, Afor stopping the valve at wide open position, the lever having also an adjustable abutment in thel form .of a stop screw, 55, set througha lug, 56, for

' encounter with the abutment, '53, at the desired limit 'of closing movement, determined by the adjustment of said screw; An anterior throttle. is indicated at with the usual operating means and connection lfor the customary function of such anterior throttle.

An important characteristic and feature of this type of carburetor is `the provision of sub-atmospheric pressure connection from a point beyond the posterior throttle valve to the liquid fuel source or path of delivery; whereby, under certain conditions the fuel may be drawn directly into the manifold 'bypassingboth the throttle valve and the mixing chamber of thecarburetor; and for this purpose a bore, 70, is made from the inner end ofthe unitary casting extendingin the general direction of the slope of the discharge element of the Venturi passage, to a point of intersection with a second bore, 71, directed in from the lower side of the casting opposite the constriction, 11, ofthe Venturi passage, said bore, 71, reaching and connecting withthe fuel discharge passage, 27. The outer ends of the bores, 7() and 71, are closed by plug, and a valve, 71a, respec tively, and a bore, 72, is made from the inner side of the 'conduit at a point just beyond the lseating position of the posterior throttle valve, into the bore, 70, wherebyit will'be understood` there is affordedapressure` com- *munication between the fuel path leading for discharge of liquid fuel into the venturi, and the region beyond the closed throttle, which when the engine is running, however idly7 is a re ion of sub-atmospheric pressure. 0 The valve, 1, serves to regulate at will the` freedom of communication between the fuel passage from the float bowland the duct, 70. l

` It will be understood that the provision described for connecting with a source of sub- 5 atmospheric pressure the path of flow of the liquid fuel from the level-governing chamber orfloat bowl to the fuel mixture conduit at the Venturi constriction, serves the purpose of causing liquid fuel to be drawn directly from said path into the engine intake beyond the throttle 'valve when the latter is closed, or at position for idling of the engine; and that under these conditions also there may be admixture of air with the fuelfdrawn in from the Venturi constriction through the passage, 27, vreversing thel direction of flow through that passage, from that whichv occurs when the posterior throttle is open with the engine running at high speed,'causing inflow of air at high velocity through the venturi, and .consequent low pressure at the discharge "l of the passage, 27, into the venturi; For un- 'derstanding the function of this passage under idling conditions it should be borne in mind that when air is drawn through a wellformed Venturi throat or constriction in a passage, there is induced in the throat a reduction of pressure, that is proportional to the square of the velocity offlow of the air. Since -liquid discharges from a jet with the velocity proportioned to the square rootv of the pressure difference applied `to it, it will I be seen that the velocity of liquid flow from a jet discharging into a throat as in a 4car- 105 buretor, would naturally, in the absence of preventing reasons, at all times be directly` as velocity of air How-through the throat', thus giving a constant mixture proportion. This would `be the result if it were not for Pthe fact that to prevent' flooding when the engine is not running, the standing level of the fuel' must be a little distance below the" .point lat whichV the fuel is to be discharged from the nozzle or jet port, necessitatinga slight lift of the liquid to bring it to the dis-v charge point, and for the further fact that a measurable force is required to overcome the surface tension orI capillary contraction existing between the liquid and the'ter'rninal 120 surface of its discharge passage'which may properly be thought of as a-dhesionibetween the liquidand the metal.' These causes oper- Y ating to prevent the movement of the liquid in accordance with the .law stated are con- P stants,"while the pressure reduction varies as* thesquarey of the `velocity flow'and the liquidV discharge varies lwith the squareroot, of the pressure difference. It will be seen,'there fore, that the interference with the proper 1120v proportions of the mixture, .dueto the constants, and which may be takenvmto account and compensated by proportioning the pas-` sages to produce proper mixture at any-se-y lected air flow velocity, will operate lto de.

feat the proper proportions at any .materially lower velocity than that lfor which thepassages are pro drtioned. 'While, with the passages proper y designed as to form and dimensions, the head acting upon the fuel by virtue of the air fiow, may be at all times of exactly the right value to maintain constancy of mixture proportions; the effective head as represented by the actual fuel discharge, would 4be less than this applied `head by an amount equal to the sumof a head equivalent to the surface tension or adhsive force mentioned, plus the negative head due tothe slightly lowered standing level of the liquid' (the governed level of the float bowl). And since the effect of this adhesive force is small when the applied headis large, and is large when the applied head isv small, it will be seen the resistanceto. the liquid flow due to these constants, represents an increasingly l great proportion of the total as the applied head decreases.

In the present construction this defect is overcome by the adjustable by-pass communieating with the fuel discharge passage immediately at its discharge end. By virtue of the pressure drop across ,this passagel when the air flow through the Venturi 'throat is small, and the disturbance above described is maximum, the effective head can be maintained at.

suitable'value to preserve the desired` mixture proportions. Tests 'demonstrate that with this arrangement the vidling by-pass so-called, operates solely as an avenue for the removal of the liquid brought to its entrance by the pressure drop or head created in the Venturi throat by the flow of the main column-,of -air through the venturi; and that the pressure drop or. head existing at the opposite end of the fuel discharge passage is not changed, being neither increased nor reducedas a result of providing the by-pass and means fory `adjusting it as to flow capacity.

These results are obtained much more effectively in such a construction as described than when a separate jet or fuel passage is made to' supply sufficient fuel to maintain the idling mixture; for the reason that in the construction herein shown, the variation is continuous and without breaks when the desired adjustment is one involving change in .the mixture proportion with change in the salts in irregularities of the mixture vproportions and usually is sufficient to begevidenced by, irregular runningof the engine, particuly, the trap chamber, 30, will be full of liquid.

And it may be seen that the flow-restricting plug, 35,commonly called al metering plug, by means of its retardment of the flow of the fuel in response tothe engine suction, has the function of causing that upon sudden subl stantial increase of suction,-such as results fromincreasing the opening of the posterior throttle valve or closing the anterior throttle, the increased suction 'will withdraw the fuel from the trap faster than it vcan flow in through the restricted aperture,- 38; and thereby the quantity of fuelA contained in the trap will be added tothe normal supply arriving'through the metering plug, with the result of momentarily enriching the fuel mixture supplied to the engine, and causing quick acceleration of the engine. This is an important purpose of providing the fuel trap in the fuel passage from the float bowl, and the metering or flow-restricting means therein anterior to the trap.

- Upon consideration of thestructure above described, it'y will be seen that it performs the functions which characterize this type of carburetor' by means very simple and economical of construction and easy of installation.

Iv claim 1. A fuel `mixture forming and supplying device forinternal combustionengines and the like, comprising a fuel mixture conduit having an air inlet, and adapted to be connected for discharge at the engine intake,A

said conduit having in its course a fluid-flow accelerating' constriction; a level-governing Vchamber constituting the immediate liquid fuel 'source -a throttle valve in the fuel mixture conduit between the fluid-flow ac-.

celerating constriction and the engine intake; a fuel passage from the liquid level goif'ernin'g chamber constituting the soleconduit for fuel from said chamber to the fuel mixture conduit anterior to the throttle valve, and discharging thereinv proximate to the fluid flow acceleratingconstriction; a tra in the course of said sole liquid conduit'open at its upper end to atmospheric pressure, and having;` both the inlet from the levelgoverning chamber and thefoutlet toward.

the fuel mixture'conduit at lthe lower part, and a branchliquid passage leading off from 'said sole conduit at a point in the latter beerned level of the level-governing chamber,

and a fuel lowrestricting means interposed anterior to the yentrance to the trapl in the sole conduit froml the liquid level-governing f chamber to the fuel mixture conduit.-

4. In the construction defined in claim 1 the level-governing chamber and the portion of the fuel mixture conduit comprising ithe How accelerating constriction being a unitary casting, the trap chamber being in a neck of the casting connecting the level-governing chamber and the mixture conduit, and having a flow-restricting metering obstruction at the bottom, forming the entrance port at the trap, and a needle valve seated in ysaid port, having its stem extending up through the entire vertical extent of the trap chamber, and emerging from the top thereof for exterior operation.

5. Inthe construction defined in claim 1 the level-governing chamber and the portion of the fuel mixture conduit comprising the How-accelerating constriction, being :ai

unitary casting, the fuel mixture conduit `being horizontal, and the level-governing chamber being positioned adjacent to the constricted portion of said conduit, the axis of the horizontal conduit being substantially at the governed liquid level of saidl chamber, the trap chamber being formed in the neckA of the casting connecting the level-governing chamber and the mixture conduit, and having the How-restricting means at the bottom, and forming the entrance port to the trap chamber; and a needle valve seated at said port and having its stem extending up from its scat through the entire vertical extent of the trap, emerging from the upper side of said neck for exterior operation. f

G. A fuel mixture forming and supplying device for internal combusion engines comi prising a fuel mixture conduit forming an air inlet and adapted to be connected for discharge of fuel mixture at the engine intake; a level governing chamber constituting the immediate liquid fuel source, a throttle -valve in the fuel mixture conduit; a fuel passage constituting the sole conduit for fuel from the level governing. chamber to the fuel mixture conduit anterior to the throttle valve; a liquid-flow-restricting means interposed in said sole conduit anterior its discharge in the fuel mixture conduit, a tra locatedin the course of said sole condult subsequent to the liquid-tiow-restricting means, said trap being open at the upper part to atmospheric pressure and havin both its inlet from the level governing chamber and its outlet to the fuel mixture conduit located at the lower part of the trap; and a branch liquid discharge passage leading off from the said sole conduit beyond the trap and discharging in the fuel mixture conduit beyond the throttle valve.

Intestimony whereof, I have hereunto set my hand at Chicago, Illinois, this 15th day of December, 1924.

PERCIVAL S. TICE. 

